The invention relates to a fuel injection system for an internal combustion engine, in which a mechanically operated high-pressure pump feeds fuel into a common supply line (common rail) which is provided for solenoid valve-controlled injection nozzles and acts as a pressure accumulator.
A high-pressure pump which feeds fuel into a high-pressure accumulator is known from the ATZ/MTZ special publication Motor und Umwelt (Engine and Environment) 1992, page 28 et. seq. "Fuel Injection for Diesel", Toshihiko. A feed line is connected in the fuel filling phase to the pump working space from which a high-pressure line leads to the high-pressure accumulator with the intermediate connection of a non-return valve. A control line which branches off from the feed line and opens into the high-pressure line downstream of the non-return valve, contains a solenoid valve which can be opened as a function of operating parameters of the internal combustion engine and influences demand-controlled feeding of the fuel. A similar high-pressure pump is known from EP-O 243 871 A2 in which fuel is also fed via a non-return valve into a high-pressure accumulator and which also includes a control line branching off a high-pressure line and switchable by means of a solenoid valve disposed in the control line.
In the Patents Abstracts of Japan 59-3161, a line arrangement is disclosed with a branch which is in communication with the high-pressure line and has a control element for demand control and a further branch line. It has a pressure regulation valve which controls the maximum fuel pressure and via which the fuel can only flow out into the fuel supply space. This arrangement does include a common high-pressure accumulator or supply line for all the injection nozzles but is not adapted to accommodate rapid pressure changes in the common supply line in the case of rapid changes in load and r.p.m.
It is the object of the invention to provide a fuel injection system which requires little constructional outlay and which, when rapid changes in r.pm. and/or load occur, permits a rapid change in the pressure in the common supply line of the injection nozzles, adapted to the new operating state.